The overall unifying theme and long range goals of the experiments described in this proposal is their relevance to an understanding of the mechanisms involved in the regulation of gene expression. In our experiments, this general problem is considered from two points of view. The first is that of gene structure, and how the interaction of specific nucleic acid sequences with other molecules determines the regulation of gene expression. The second point of view is directed toward the general problem of genome organization, with particular reference to two aspects: a) the functional (and regulatory) implications of the arrangement of genes on the chromosome, and b) how this arrangement reflects possible mechanisms which are important in the "evolution" of a genome.